The study was carried out between November 2014 and March 2016 to determine certain morphometric characteristics of two pipefish species occurring in Lake Bafa, Syngnathus abaster and Syngnathus acus. A total of 211 pipefish were captured during the sampling, including 77 individuals of S. abaster (♀: 25; ♂: 44; immature: 8) and 134 individuals of S. acus (♀: 31; ♂: 76; immature: 27). The male-female ratios were 1:1.76 and 1:2.45, respectively. A difference was found in sex ratios between the two species (p < 0.05). The mean length of the captured fish was 86.63 ± 16.77 mm for S. abaster and 82.63 ± 16.02 mm for S. acus and the relationship between the total length and weight, referred to as the length-weight relationship, was as follows: W = 0.00000001L^3.71 (R² = 0.89), and W = 0.000000007L^3.86 (R² = 0.83), respectively. Seven morphometric characteristics were analyzed. The analyses revealed that S. acus and S. abaster were significantly different from each other in terms of their body depth (p = 0.006; p < 0.05), mouth width (p = 0.004; p < 0.05) and height (p = 0.008; p < 0.05). High correlation values were obtained for TL/BD and TL/HD in S. abaster and S. acus, respectively (r > 1). In conclusion, among the congeneric species occurring in Lake Bafa, S. abaster and S. acus are characterized by a shorter head length and total length compared to their sea counterparts.

We, here, aimed to determine the presence of Anguillicola crassus, a swim bladder parasite, in 89 (male: 45, female: 44) dead European eel specimens obtained seasonally between 2020-2021 from a regional fisherman, who has fished with fyke net in the locality Tuzla of Izmir Bay, Eastern Aegean Sea. Out of 21 male European eels caught in winter, only one specimen (TL: 48.5 cm and TW: 247.12 g) had 23 swim bladder parasites (adult nematodes: 15, larvae: 8) and similarly, only one parasite was found in one specimen (TL: 37.5 cm and TW: 88.47 g) of 8 eels caught in spring. No parasite was found in the female eels. At the examinations, it was determined that all adult Anguillicola crassus specimens were females and the minimum-maximum and average length values in adult and larval parasites were, respectively, 1.5-2.5 cm (1.99 ± 0.31) and 0.7-1.3 cm (1.025 ± 2.40). Consequently, the species A. crassus, a swim bladder parasite, was found in European eels from the locality Çamalti Tuzla in two seasons (winter and spring) and this parasitic nematode were only in male eels. This study is a first and remarkable one having evidential value, which shows the presence of the species A. crassus among the eel population in the locality Çamalti Tuzla of Izmir Bay. Besides, it is a population that should be monitored due to the status of Anguilla anguilla on the IUCN red list.

Sardina pilchardus is a multiple spawning fish, i.e., the species that spawns periodically during the spawning period. In order to examine the reproduction biology of the species, the specimens were obtained in the known spawning period indicated by the current literature obtained from fishers who were commercially fishing in December 2018 and January-February 2019. After the fork length and total length together with their weight measurements, the specimens were dissected in the laboratory. The adult females‘ gonads were then fixed in 4% formalin solution for fecundity. A total of 170 individuals was examined and the values of their fork length, total length and weight were computed as 9.7-13.4 cm (mean: 11.16±0.81), 10.5-15 cm (mean: 12.3±0.89), 8.06-23.7 g (mean: 12.7±2.93), respectively. 44 of the supplied specimens were male (25.9%), 122 female (71.8%) and 4 (2.3%) uncertain, thus, the female: male ratio was determined as 2.77:1. According to χ2 test results, a statistically significant difference was observed among individuals. For the specimens examined, the fork length-weight relationship was calculated as W = 0.0098FL2.96, while total length-weight relationship was W = 0.0071TL2.97. In order to calculate the fecundity, sub-samples were taken from the anterior, median and posterior parts of 15 ovaries in the ration of 2 - 5% of the ovary weight and the mature oocytes were counted. As a result, the species‘ fecundity was found to be between 4,600-9,800 (6,110±1,755). The relationship between total length and fecundity was computed as W= 1,640.7 TL-13,907 and a linear relationship was determined.

The Lessepsian migrants of the family Fistulariidae, which are widely distributed in the Eastern Mediterranean coasts of Türkiye, are represented by two species, Fistularia commersonii and Fistularia petimba. This study focused on estimating various biological indices of red cornetfish Fistularia petimba Lacepède 1803, eastern Mediterranean coast of Türkiye. The biological indices determined were: FI- Fullness index, HSI-Hepatosomatic index, GSI-Gonadosomatic index, EQ-Encephalization quotient, VSI-Visceral index, IWL-Zihler index, Fulton-K: Fulton-Condition. For this study, 65 red cornetfish specimens (♀:40, ♂:23, immature: 2) caught as by-catch in the nets of commercial trawlers, operating in the study area in the winter of 2021 were studied. The estimated length-weight relationship (LWR) was W=0.0001L3.34 (R2= 0.89) and the species exhibits a positive allometric growth. The mean index (M±SD) and range values calculated from the obtained data are as follows: FI 1.05±0.13 (0.83-1.26); HSI 0.43±0.05 (0.23-0.62); GSI 1.27±0.20 (1.08-1.46); EQ 0.0024±0.0003 (0.0022-0.0025); VSI 3.14±0.39 (2.08-4.20); IWL 12.37±1.54 (4.41-20.3) and Fulton-K 0.47±0.06 (0.43-0.51). According to these results, it can be hypothesized that this Lessepsian species is well established and thrives in the eastern Mediterranean coasts of Türkiye. Although it is evaluated as the least concern category (LC) in the IUCN Red List 2013, we believe that the species has an invasive potential. Therefore, this study, in which biological index parameters were presented for Fistularia petimba, may be important in terms of fisheries management, planning measures to reduce distribution and combating invasiveness.

Pipefishes (Family Syngnathidae) are representative fishes in many European coastal areas asso-ciated with vegetal assemblages and other shallow habitats. The polyandrous pipefishes Syngnathus abaster and S. acus co-occur in Metruk Tuzla (Bargilya Wetland, Aegean Sea, Turkey), a protected but threatened wetland due to anthropogenic disturbances. Both species were sam-pled during the breeding season (April-2018 and June-2019) for the assessment of growth and trophic features revealed from stable isotope profiles (δ13C and δ15N) and gut content. Both species showed positive allometric growth, with similar length-weight relationships. The isotope approach indicated that both species occupy similar trophic niches, with mean δ13C and δ15N values of -17.0 ± 1.2 ‰ for δ13C and 13.2 ± 0.6 ‰ for δ15N in S. abaster, and -17.3 ± 1.2 ‰ for δ13C and 13.3 ± 0.7 ‰ for δ15N in S. acus. The niche area for all sex types (undifferentiated specimens, males and females) in S. acus was slightly broader than in S. abaster. The simulation analysis of the trophic position (TP) in both species agreed with the isotopic assessment (TP = 3.67 ± 0.61 in S. abaster and 3.46 ± 0.66 in S. acus). Despite the high trophic resemblance between S. abaster and S. acus, the gut content assessment revealed the large contribution of copepods (especially Calanipeda aquaedulcis) to the dietary regime in both pipefishes. However, while the diet in S. abaster seemed to be almost monospecific, cladocerans were also an important resource in S. acus. Hence, we suggest that potential inter-specific competition for dietary resources would be minimized likely due to the occupancy of different microhabitats, a hypothesis that needs to be confirmed by further research.